Luminaire housings are frequently used in the lighting industry, such as in hazardous locations. UL (Underwriters Laboratories Inc.) and CSA (Canadian Standards Association) have stringent requirements regarding the mechanical strength of luminaire housings, particularly non-metallic luminaire housings. Those standards are even more difficult to meet when power is supplied through a rigid power supply or conduit. A rigid conduit imparts more mechanical loads and stresses to the luminaire housing than a flexible conduit. These mechanical loads and stresses include torque, tension and bending loads. The requirements are based on worst case loads being applied to the conduit/hub attachment portion of the luminaire housing during the installation process.
Luminaire housings are generally thin-walled and light-weight structures that are susceptible to damage. Thus, non-metallic and thin-walled metallic luminaire housings are especially prone to damage if they are not able to handle the mechanical loads and stresses imparted by the power supply conduit. The likelihood of damage is even greater when power is supplied through a rigid conduit since there is no flexibility in the conduit to absorb some of the mechanical loads and stresses, thereby passing all the mechanical loads and stresses into the luminaire housing. Non-metallic and thin-walled metallic luminaire housings are highly susceptible to breaking under these mechanical loads and stresses, which could also cause injury to personnel working in the area as well as possibly damaging the electrical system.
One possible solution to strengthening luminaire housings is to make the luminaire housings more rigid by such means as increasing the thickness of the housing walls or strengthening the mounting hardware. However, to do so results in a luminaire housing that is more complex and expensive to manufacture, particularly the increased cost of the fixture housing and tooling costs. Furthermore, increasing the thickness of the housing walls increases the weight of the luminaire assembly, as well as increasing the mechanical structures needed to support the luminaire assembly. A need exists for a luminaire housing assembly that is able to handle the mechanical loads and stresses imparted by the electrical power supply, while remaining relatively inexpensive and easy to manufacture.
Examples of existing brackets for supporting luminaire housings are disclosed in the following U.S. Pat. No. 3,739,319 to Garnett; U.S. Pat. No. 4,062,470 to Boteler; U.S. Pat. No. 4,138,716 to Muhlethaler et al.; U.S. Pat. No. 4,379,321 to Plemmons et al.; and U.S. Pat. No. 6,207,894 to Reiker.
Thus, there is a continuing need to provide improved luminaire housing assemblies.